7,881 research outputs found
Exact reconstruction with directional wavelets on the sphere
A new formalism is derived for the analysis and exact reconstruction of band-limited signals on the sphere with directional wavelets. It represents an evolution of a previously developed wavelet formalism developed by Antoine & Vandergheynst and Wiaux et al. The translations of the wavelets at any point on the sphere and their proper rotations are still defined through the continuous three-dimensional rotations. The dilations of the wavelets are directly defined in harmonic space through a new kernel dilation, which is a modification of an existing harmonic dilation. A family of factorized steerable functions with compact harmonic support which are suitable for this kernel dilation are first identified. A scale-discretized wavelet formalism is then derived, relying on this dilation. The discrete nature of the analysis scales allows the exact reconstruction of band-limited signals. A corresponding exact multi-resolution algorithm is finally described and an implementation is tested. The formalism is of interest notably for the denoising or the deconvolution of signals on the sphere with a sparse expansion in wavelets. In astrophysics, it finds a particular application for the identification of localized directional features in the cosmic microwave background data, such as the imprint of topological defects, in particular, cosmic strings, and for their reconstruction after separation from the other signal component
Suppressed antinodal coherence with a single d-wave superconducting gap leads to two energy scales in underdoped cuprates
Conventional superconductors are characterized by a single energy scale, the
superconducting gap, which is proportional to the critical temperature Tc . In
hole-doped high-Tc copper oxide superconductors, previous experiments have
established the existence of two distinct energy scales for doping levels below
the optimal one. The origin and significance of these two scales are largely
unexplained, although they have often been viewed as evidence for two gaps,
possibly of distinct physical origins. By measuring the temperature dependence
of the electronic Raman response of Bi2Sr2CaCu2O8+d (Bi-2212) and HgBa2CuO4+d
(Hg-1201) crystals with different doping levels, we establish that these two
scales are associated with coherent excitations of the superconducting state
which disappears at Tc. Using a simple model, we show that these two scales do
not require the existence of two gaps. Rather, a single d-wave superconducting
gap with a loss of Bogoliubov quasiparticle spectral weight in the antinodal
region is shown to reconcile spectroscopic and transport measurements.Comment: 3 figure
Automated Incubation and Digital Image Analysis of Chromogenic Media Using Copan WASPLab Enables Rapid Detection of Vancomycin-Resistant Enterococcus.
Objective: The aim of the present study was to assess whether the WASPLab automation enables faster detection of vancomycin-resistant Enterococcus (VRE) on chromogenic VRE-specific plates by shortening the incubation time. Methods: Ninety different VRE culture negative rectal ESwab specimens were spiked with various concentrations (ranging from 3 × 10 <sup>2</sup> to 3 × 10 <sup>7</sup> CFU/ml) of 10 Enterococcus faecium strains (vancomycin MICs ranging from 32 to >256 mg/l), 3 E. faecium VanB strains (vancomycin MICs: 4, 8, and 16 mg/l), and 2 E. faecium VanB strains displaying vancomycin heteroresistance (vancomycin MICs: 64 and 96 mg/l). Results: Besides the two strains exhibiting vancomycin heteroresistance, all the other 13 VRE strains included in this study were detected as early as 24 h on the WASPLab even if the inoculum was low (3 × 10 <sup>3</sup> CFU/ml). When the vancomycin MICs were high, all strains were detected as early as at 18 h. However, 30 h was a conservative time point for finalizing the analysis of chromogenic cultures. Conclusion: These results suggested that the WASPLab automated incubation could allow decreasing the initial incubation time to 18 h, followed by an intermediate time at 24 h and a final incubation period of 30 h for VRE culture screening, to deliver rapid results without affecting the analytical sensitivity
Statistical Quantile Learning for Large, Nonlinear, and Additive Latent Variable Models.
The studies of large-scale, high-dimensional data in fields such as genomics and neuroscience have injected new insights into science. Yet, despite advances, they are confronting several chal- lenges, often simultaneously: lack of interpretability, nonlinearity, slow computation, inconsistency and uncertain convergence, and small sample sizes compared to high feature dimensions. Here, we propose a relatively simple, scalable, and consistent nonlinear dimension reduction method that can potentially address these issues in unsupervised settings. We call this method Statistical Quantile Learning (SQL) because, methodologically, it leverages on a quantile approximation of the latent variables together with standard nonparametric techniques (sieve or penalyzed methods). We show that estimating the model simplifies into a convex assignment matching problem; we derive its asymptotic properties; we show that the model is identifiable under few conditions. Compared to its linear competitors, SQL explains more variance, yields better separation and explanation, and delivers more accurate outcome prediction. Compared to its nonlinear competitors, SQL shows considerable advantage in interpretability, ease of use and computations in large-dimensional set- tings. Finally, we apply SQL to high-dimensional gene expression data (consisting of 20, 263 genes from 801 subjects), where the proposed method identified latent factors predictive of five cancer types. The SQL package is available at https://github.com/jbodelet/SQL
A Comparison of Methods for Determining the Molecular Content of Model Galaxies
Recent observations indicate that star formation occurs only in the molecular
phase of a galaxy's interstellar medium. A realistic treatment of star
formation in simulations and analytic models of galaxies therefore requires
that one determine where the transition from the atomic to molecular gas
occurs. In this paper we compare two methods for making this determination in
cosmological simulations where the internal structures of molecular clouds are
unresolved: a complex time-dependent chemistry network coupled to a radiative
transfer calculation of the dissociating ultraviolet (UV) radiation field, and
a simple time-independent analytic approximation. We show that these two
methods produce excellent agreement at all metallicities >~10^-2 of the Milky
Way value across a very wide range of UV fields. At lower metallicities the
agreement is worse, likely because time-dependent effects become important;
however, there are no observational calibrations of molecular gas content at
such low metallicities, so it is unclear if either method is accurate. The
comparison suggests that, in many but not all applications, the analytic
approximation provides a viable and nearly cost-free alternative to full
time-dependent chemistry and radiative transfer.Comment: 8 pages, 7 figures, accepted to ApJ, emulateapj format. This version
contains typo corrections and changes to figure presentation, but is
otherwise the same as the previous versio
Study of the microstructure resulting from brazed aluminium materials used in heat exchangers
Re-solidification of AA4343 cladding after brazing as well as the related precipitation in the modified AA3003 core material have been investigated. Analysis of the re-solidified material showed that partial dissolution of the core alloy occurs in both the brazing joints and away of them. Far from the brazing joints, the dissolution is, however, limited and diffusion of silicon from the liquid into the core material leads to solid-state precipitation in the so-called “band of dense precipitates” (BDP). On the contrary, the dissolution is enhanced in the brazing joint to such an extent that no BDP could be observed. The intermetallic phases present in the resolidified areas as well as in the core material have been analyzed and found to be mainly cubic alpha-Al(Mn,Fe)Si. These results were then compared to predictions made with available phase diagram information
Genome-wide transcription analysis of clinal genetic variation in Drosophila.
Clinal variation in quantitative traits is widespread, but its genetic basis awaits identification. Drosophila melanogaster shows adaptive, clinal variation in traits such as body size along latitudinal gradients on multiple continents. To investigate genome wide transcription differentiation between North and South that might contribute to the clinal phenotypic variation, we compared RNA expression patterns during development of D. melanogaster from tropical northern and temperate southern populations using whole genome tiling arrays. We found that genes that were differentially expressed between the cline ends were generally associated with metabolism and growth, and experimental alteration of expression of a sample of them generally resulted in altered body size in the predicted direction, sometimes significantly so. We further identified the serpent (srp) transcription factor binding sites to be enriched near genes up-regulated in expression in the south. Analysis of clinal populations revealed a significant cline in the expression level of srp. Experimental over-expression of srp increased body size, as predicted from its clinal expression pattern, suggesting that it may be involved in regulating adaptive clinal variation in Drosophila. This study identified a handful of genes that contributed to clinal phenotypic variation through altered gene expression level, yet misexpression of individual gene led to modest body size change
Summary report of the Standards, Options and Recommendations for malnutrition and nutritional assessment in patients with cancer (1999)
The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica
The ASTEP (Antarctica Search for Transiting ExoPlanets) program was
originally aimed at probing the quality of the Dome C, Antarctica for the
discovery and characterization of exoplanets by photometry. In the first year
of operation of the 40 cm ASTEP 400 telescope (austral winter 2010), we
targeted the known transiting planet WASP-19b in order to try to detect its
secondary transits in the visible. This is made possible by the excellent
sub-millimagnitude precision of the binned data. The WASP-19 system was
observed during 24 nights in May 2010. The photometric variability level due to
starspots is about 1.8% (peak-to-peak), in line with the SuperWASP data from
2007 (1.4%) and larger than in 2008 (0.07%). We find a rotation period of
WASP-19 of 10.7 +/- 0.5 days, in agreement with the SuperWASP determination of
10.5 +/- 0.2 days. Theoretical models show that this can only be explained if
tidal dissipation in the star is weak, i.e. the tidal dissipation factor Q'star
> 3.10^7. Separately, we find evidence for a secondary eclipse of depth 390 +/-
190 ppm with a 2.0 sigma significance, a phase consistent with a circular orbit
and a 3% false positive probability. Given the wavelength range of the
observations (420 to 950 nm), the secondary transit depth translates into a day
side brightness temperature of 2690(-220/+150) K, in line with measurements in
the z' and K bands. The day side emission observed in the visible could be due
either to thermal emission of an extremely hot day side with very little
redistribution of heat to the night side, or to direct reflection of stellar
light with a maximum geometrical albedo Ag=0.27 +/- 0.13. We also report a
low-frequency oscillation well in phase at the planet orbital period, but with
a lower-limit amplitude that could not be attributed to the planet phase alone,
and possibly contaminated with residual lightcurve trends.Comment: Accepted for publication in Astronomy and Astrophysics, 13 pages, 13
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